2020牛客寒假算法基础集训营4-D子段异或

思路

　　

CODE

 #include <bits/stdc++.h>
 #define dbg(x) cout << #x << "=" << x << endl

 using namespace std;
 typedef long long LL;

 template<class T>inline void read(T &res)
 {
     char c;T flag=;
     while((c=getchar())<''||c>'')if(c=='-')flag=-;res=c-'';
     while((c=getchar())>=''&&c<='')res=res*+c-'';res*=flag;
 }

 namespace _buff {
     const size_t BUFF =  << ;
     char ibuf[BUFF], *ib = ibuf, *ie = ibuf;
     char getc() {
         if (ib == ie) {
             ib = ibuf;
             ie = ibuf + fread(ibuf, , BUFF, stdin);
         }
         return ib == ie ? - : *ib++;
     }
 }

 int qread() {
     using namespace _buff;
     int ret = ;
     bool pos = true;
     char c = getc();
     for (; (c < '' || c > '') && c != '-'; c = getc()) {
         assert(~c);
     }
     if (c == '-') {
         pos = false;
         c = getc();
     }
     for (; c >= '' && c <= ''; c = getc()) {
         ret = (ret << ) + (ret << ) + (c ^ );
     }
     return pos ? ret : -ret;
 }

 const int maxn = 2e5 + ;

 map <int, int> mapp;
 int a[maxn];
 int n;
 int xorsum[maxn];

 int main()
 {
     read(n);
     for(int i = ; i <= n; ++i) {
         read(a[i]);
         xorsum[i] = xorsum[i-];
         xorsum[i] ^= a[i];
     }
     mapp[] = ;
     LL ans = ;

     for(int i = ; i <= n; ++i) {
         if(mapp[xorsum[i]]) {
             ans += mapp[xorsum[i]];
         }
         mapp[xorsum[i]]++;
     }
     cout << ans << endl;
     return ;
 }